1. Field of the Invention
The present invention relates to a hydrostatic extrusion press and to the structural features of a die useful therein. The press is particularly designed for extruding non-round products, in particular to compound products having a core of one material and a casing of another material, such as copper-clad aluminium bars.
2. The Prior Art
In the extrusion of copper-clad aluminium bars, irregularities will in certain cases appear at the surface as a result of the fact that pressure medium on the billet surface accompanies this surface from the pressure chamber down into the die and is collected between the die surface and the billet surface. When a certain quantity has been collected between the billet surface and the die surface at the portion nearest the die opening, the pressure medium is pressed out through the die opening between its inner surface and the material of the billet. Because of the high pressure, the pressure medium is pressed out at a great speed and causes damage in the form of spots on the surface of the product or, in the worst case, breaks through the copper layer. The problems seem to be most prominent in the extrusion of profiles with a high aspect ratio, and in the case of a small extrusion ratio.